The present invention relates to protective covering of plastic or metal parts, and more particularly, the invention relates to the protection of such construction parts in aircraft against damage, for example, from lightening.
Since plastic parts have relatively light weight they are used to an increasing extent. These plastic parts are, of course, usually electrical insulators. Unfortunately, the employment of insulative plastics reduces the safety aspect as far as lightening is concerned. Aircrafts are inherently endangered by lightening, and when hit, some damage is caused particularly because of the concentration of structure parts in the limited space of the craft. That damage is the greater the more parts are made of low conductive material. Therefore, the problem exists to protect such plastic parts against lightening.
It is known generally to discharge electrostatic charges of plastic parts, for example, by means of so-called antistatic coatings. It has also been proposed to metal-coat such plastic parts so as to obtain continuous electrically conductive paths.
Various procedures have been proposed to apply a metal coat to such plastic parts, for example, by means of flame-spraying, galvanizing (plating), or by means of chemical deposition and precipitation or by bonding foils to these plastic parts. The surface of the plastic part has to be pretreated in either case to obtain satisfactory adhesion between the part to be protected and the cover, coating, lining, etc.
It is not believed that the problem outlined above has been satisfactorily solved thus far. The problem is compounded by the fact that such construction parts for aircraft which are exposed to the environment should be made erosion proof, because high speed water droplets have quite extensively a corroding effect. Still additionally, the construction parts should not be penetrated by moisture.